Electric switch construction



2 Shee'ts-Sheet 1 Filed April 26, 1946 fm/cnior N M w 9 3 Firs. 4

March 29, 1949. H. MILLARD ELECTRIC SWITCH CONSTRUCTION 2 Sheets-Sheet 2 Filed April 26, 1946 Pie. 6

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Patented Mar. 29, 1949 v 2,465,654 ELECTRIC SWITCH CONSTRUCTION Harper Millard, Freeport, Ill., assignor to First Industrial Corporation, Wilmington, Del., a

corporation of Delaware Application April 26, 1946, Serial No. 665,029

8 Claims. (Cl. 173-324) This invention relates generally to electric switches and has particular reference to an improved means for connecting the component parts.

A specific object of this invention lies in the provision of a novel rivet construction for mounting contact and terminal members onto insulator or switch housing wall portions.

Many previous attempts have been made to assemble the switch contacts and terminal members by means of rivets as it has long been recognized that a great saving in assembly time and switch costs would be efiected by using rivets instead of the conventional bolts and screws. None of the previous rivet constructions have been entirely satisfactory for use with the compact precision type of switch (for example, such as that illustrated by Patent No. 2,351,181, dated June 13, 1944, toLouis W. Bangasser). In this type i switch, attempts to hold a contact member and its corresponding terminal member pressed respectively against inner and outer surfaces of the housing wall or insulating mounting plate have met with failure due to the great difference between the temperature coefilcient of the metallic contact and terminal members and that of the plastic wall or plate so that after the switch was subjected to heating and cooling a few times in service, the riveted joint would be loosened sufiiciently to increase its electrical resistance and otherwise impair the operating characteristics of the switch. This is caused by the relative stiffness of the conventional riveted construction and accordingly the present invention has been evolved in the development of a riveted switch construction which would be simple and economical and at the same time possess sufilcient inherent resilience that the differential expansion characteristics of the abutting metal and plastic parts within the riveted connection would not cause it to be loosened.

Other objects and advantages of the present invention will be apparent in the following description in connection with the accompanying drawing, in which- Figure 1 is a longitudinal sectional elevational view of a complete snap switch embodying the present invention;

Fig. 2 is a transverse sectional, elevational view of Jane: switch of Figure 1 taken along the lines of i Fig. 3 is a transverse sectional. elevational view of the switch of Figure 1 taken along the lines of 3-3;

Fig. 4 is an enlarged sectional view of one of the stationary contact-terminal assemblies shown in Fig. 3 as the parts appear before compressing the rivets;

Fig. 5 is a view similar to Fig. 4 showing the rivet compressed to hold the contacts and terminals tightly together on opposite sides of the wall;

Figs. 6 and '7 are similar, respectively, to Figs. 4 and 5, but showing a modified construction, and

Fig. 8 is an enlarged view of another modification.

The details of the construction and operation of the precision type snap acting switch shown in Figure 1 to illustrate the present invention may be found in the above-mentioned Patent No. 2,351,181. Briefly, for the purposes here, the switch consists of a housing 2| of insulating material having a spring member 22 carrying a movable contact 23 between stationary contacts 24 and 26. At the end opposite the movable contact the spring 22 is suitably mounted upon a U- shaped anchor or contact member 27 so as to snap the contact 23 from one of the stationary contacts to the other when moved by the operatin plunger 28.

As shown in Fig. 2, a rivet 29 according to this invention is employed to hold together the terminal 3i, anchor 21, and the end of the spring 22. At the opposite end of the switch, as shown in Fig. 3, a rivet 33 maintains the contact 26 and the terminal 34 pressed tightly against opposite sides of the insulating switch wall 2|; and a similar but somewhat longer rivet 36 maintains the contact 24 and the terminal 31 pressed tightly against opposite sides of the switch wall.

The invention will first be considered in connection with the rivet 33, shown enlarged in Fig, 4. The head portion 38 is initially formed with a frusto-conical bearing or similar shaped surface 39 and the end of the rivet opposite the head will have a hollow portion ll extending through the contact 26 and for a substantial distance into the wall 2| of the switch housing. Aligned apertures 42, 43, and 44 will be formed, respectively, in the contact, switch wall, and terminal to receive the rivet. Axial compression of the rivet 33 in one quick, simple operation will fasten the parts together as shown in Fig. 5 where the headed portion 38 is flattened out against the terminal 34, the end of the hollow portion 4| is flanged out over the contact 25 as shown at 46. and the hollow portion 4| is expanded radially into very tight frictional engagement with the contact apertures 42 and th housing aperture 43. The flattening of the rivet head in this manner gives the rivet a certain amount of resilience, thereby placing the rivet under an added tension due to the energy stored in the head tending to return it to a frusto-conical shape. The hol low portion 4i ordinarily does not expand uniformly, thereby forming corrugations such as indicated at 61. These corrugations lend resilience to the rivets and the longitudinal flexibility so obtained permits the parts to be held tightly together even in the event there be some 'dimensional change due to aging or temperature change. Another advantage of radially expanding the rivet in this manner is that it fills the aperture through which it passes, thus accurately locating the parts with respect to one another and holding them in such relationship. The eifectiveness of this radial expansion may be illustrated by disassembling a model of a switch so riveted and breaking away the switch wall 2i. It will then be found that the rivet has been pressed into such tight engagement with the contact bore'42 that it is very difiicult to loosen the hold of the rivet on the contact.

It will be noted that, in the modification shown, the rivet head is in engagement with the terminal, outside the switch, in each case. This is done only because it improves the appearance of the switch and if desired for any other reason the rivet head may be reversed to bear against the contact for it will function equally well in either position. Furthermore, while I have shown in Figs. 4 and 5 enlarged views of the rivet 33, obviously the description for it will apply to the other rivet 36 for their constructions are identical with the exception that 36 is somewhat longer than 33,

The riveted construction at the spring-mounted end of the switch, shown in Fig, 2, is substantially the same in principle as that already described in connection with rivets 33 and 36. In this case, when the rivet 29 is compressed, the hollow end portion 62 will be expanded radially into tight frictional engagement with the switch housing 2|, the anchor 21, and the spring member 22. The axially aligned bores of the terminal, housing, anchor, and spring may be all substantially the same size, as are the aligned bores in Fig. 4, or some may be counterbored for improved interlocking as will be described subsequently in connection with Fig. 8.

For certain conditions of service, the riveted construction for the stationary contacts will take the form shown in Figs. 6 and 7 where a some what more positive means of interlocking the parts is shown. The housing bore 43 is enlarged by the counterbore 59 and the counterbore itself is further enlarged by the flared end portion 6| to provide a substantial recess between the contact 26 and the housing 2|, The hollow portion M of the rivet extends preferably down to the bottom of the counterbore 59. As shown in Fig. 7, when the rivet is compressed, the frusto-conical shaped head 38 will be flattened upon the terminal 34, as above described in connection with Figs. 4 and 5, and the hollow portion 4| will be expanded radially into tight, frictional engagement with the counterbore 59, a portion of which will be expanded into the space provided by the flare 6i whereby the parts will be positively prevented; from up and down or sidewise movement with, respect to one another, yet enough energy will be stored up within the corrugations 41 and also in the flattened-out head portion 38. that the con nection will remain tight even in the event of dimensional change of the parts. i

This same type of counterbored construction may be applied to the anchor .end of the switch,

as shown in Fig. 8. In this case, the washer 32, the switch wall 2i. and the terminal 3| will be provided with bores 66, 61, and 68, respectively, which are initially slightly greater than the diameter oi the rivet 29. The spring 22, anchor 21, and a portion of the switch housing 2| will be provided with a common counterbore 10 and, when the rivet is compressed axially, the flange 46 will be lapped over the top of the washer 32, and the initially frusto-conical headed portion 38 will be flattened upon the terminal ii. The hollow portion 62 of the rivet will be expanded radially into engagement with the washer bore 66 and the common counterbore 10 whereby all the parts will be held firmly together.

It will be readily apparent that the embodiments of the present invention are by way 01 illustration and example only and that such embodiments are capable of numerous variations and modifications. Specific arrangement of parts are used only to facilitate description and are not intended'as limitations of the invention.-

I claim:

1. In an electric switch, the combination of an insulator, contact and terminal members separated by said insulator, a headed rivet extending through aligned apertures formed in said members and said insulator, said'rivet having a tubular portion opposite the head thereof, said tubular portion being flanged to engage an outer surface of one of said members and being radially expanded at spaced positions to engage the side walls forming the apertures in said one member and said insulator, the head of said rivet having a portion fiexed in the direction away from the tubular portion by engagement of the head with the other of said members short of its elastic limit to store energy therein tending to stress said rivet in tension wherebyto positively maintain said insulator, contact and terminal members in tightly assembled relation under all service conditions.

2. In an electric switch assembly, the combination of a first member formed from substantially non-resilient insulating .material, conducting members separated by said first member, said members having aligned apertures formed therein, and a rivet disposed in said apertures for mechanically and electrically connecting said members in fixed relation including a head engaging one of the conducting members, and a shank, said shank having a tubular portion extending for a substantial part of its length fiared' on its end opposite the head to engage the other conducting member on the side of the assembled members away from the head, said tubular portion being positioned in said aligned apertures and expanded radially at spaced positions to form corrugations providing excess metal in the tubu'- lar portion adapted to flex without substantial plastic deformation of the unit and thereby store energy when the combined thickness of the first member and the conducting members increases to a greater extent than the length of the'rivet to maintain said conducting members and said rivet in a positive electrical conducting relation upon contraction of the parts.

3. In an electric switch assembly, the combination of a first member formed from insulating material, conducting members'separated by said first member, said members having aligned apertures formed therein, and a rivet having a head engaging one of the conducting members and in its free state having a frusto-conical bearing surface on its underside tapering outwardly and away from the head end thereof, said rivet having a tubular portion extending for a substantialpart of its length and flared on its outer end to engage the other or the conducting members on the side of the assembled members away from the head, said tubular portion being positioned in said aligned apertures and expanded radially at spaced positions to form corrugations engageable with the side walls of the apertures, said head in the assembled state being pressed against said one conducting member with sufllcient force to flex the irusto-conical bearing surface to a plane state to stress the rivet and thereby maintain the riveted assembly in a tightly riveted condition.

4. In an electric switch, the combination of an electrical insulating member, electrical conductllig members separated by said insulating member, said members being in an assembled relation and having aligned bores, said insulating member bein counterbored, a rivet extending through said members and having a head engaging one side of the assembly, said rivet having a tubular portion extending a substantial part of its length and flared at its outer end into engagement with the side of the assembly away from the head, said head having a.portion biased in the direction away from the tubular portion by contact with one side of the assembly to store energy tending to keep said rivet in a stressed condition, said tubular portion being positioned in said bores and counterbore and buckled to form corrugations engageable with the side walls of the bore and counterbore, said corrugations coacting with said head in storing energy tending to exert compressive forces between said head on one side of the assembly and said flared end on the other side of the assembly whereby to maintain said members in a tightly assembled relation under all service conditions of the switch.

5. In an electric switch, the combination of an insulator, first and second conducting members separated by said insulator, said members and said insulator having axially aligned bores, said insulator bore having a counterbore flared at an end beneath the first of said members, and a rivet having a head engaging one side of the second member and having a portion flexed longitudinally f the rivet by engagement with said second member in a direction to store energy therein and stress the rivet in tension, said rivet having a shank positioned within said bores and flared at its outer end to engage one side of said first member, said shank including a tubular portion extending from the flared end substantially to that part of said rivet adjacent the bottom of said counterbore, said tubular portion being axially deformed to produce corrugations engaging the confining side walls of said counter-bore and engaging the under surface of the first member adjacent the flared end of said counterbore to positively secure the first member in position and to provide excess metal in the tubular portion adapted to flex and store energy without substantial plastic deformation of the rivet when the combined thickness of the insulator and the conducting members increases to a greater extent than the length of the rivet to retain the respective members in a tightly assembled relation upon contraction of the parts.

6. In an electric switch, the combination of a switch support formed from non-resilient insulating material, first and second conducting members being separated by said support, said members and said support having axially aligned holes. said support hole being larger on one side of the support than on the other to form a shoulder at an intermediate portion or said hole, and a rivet extending through said holes to secure said members and said support in tightly assembled relation. said rivet having a shank provided with a tubular portion flared at its outer end to engage one side of the first member, said tubular portion being radially expanded to form corrugations, one of said corrugations engaging the first member adjacent the enlarged end of said hole in the support to positively secure the first member and the rivet in a mechanically tight and a positive electrical conducting relation, and another of said corrugations engaging said shoulder, said corrugations being resilient to the extent of tending to return to their initial configuration in the counterbore when a tensile force is applied at opposite ends of the corrugated .portion, said rivet having a head engaging one side of the second member provided with a portion flexed longitudinally of the rivet by engagement with the second member to store energy tending to return the portion to its original configuration whereby a compressive force is exerted between the shoulder and the second conducting member to positively retain the respective members in a mechanically tight and a positive electrical conducting assembled relation in the event of dimensional changes of the respective members.

7. In an electric switch, the combination of a support formed from non-resilient insulating material, first and second conducting members on opposite sides of said support, said members and said support having axially aligned holes, said support hole being larger on one side of the support than on the other to form a shoulder at an intermediate portion of said hole, said enlarged portion of said hole being flared at its outer end, and a rivet extending through said holes to secure said members and said support in a tightly assembled relation, said rivet having a shank with a tubular portion flared at its outer end to engage one side of the first member, said tubular portion being formed from resilient metal and being radially expanded to form corrugations, a first of said corrugations being received in said flared portion of the hole in the support and abutting against the first member adjacent the flared end of said hole for clamping the first member and the rivet in a mechanically tight and a positive electrical conducting relation, and a second oft said corrugations engaging said shoulder, said rivet having a head engaging one side of the second member and coacting with the second corrugation to secure the respective parts in a tightly assembled relation, said head in the free state of the rivet having a portion extending toward the shank of the rivet, said portion in the assembled position of the rivet being flexed in the direction of the head of the rivet, said head being formed from resilient material and on flexing of said portion storing energy tending to exert a compressive force between the shoulder and the second conducting member to positively retain the respective members in a mechanically tight and a positive electrical conducting assembled relation.

8. In an electric switch, the combination of a support formed from non-resilient insulating material, and having a hole extending therethrough, said hole being larger on one side than on the other to form a shoulder at an intermediate portion, a. first conducting member mounted on one side of said support and having a hole in alinement with the .enlarged end or said hole in the support, said hole in the first conducting member being smaller than the enlarged end or the hole in the support so that a portion of said first conducting member overlies said enlarged end of the hole. a second conducting member mounted on the opposite side of said support and having ahole in alinement with said hole in the supp rt; said hole in the second conducting member being substantially the same size as the smaller end or the hole in the support, and a. rivet extending through said holes to secure said members and said support in a tightly assembled relation, said flanged to engage one side of the first member, said tubular portion being radially expanded to form conngations, one of said corrugations abutting against the portion of the first member overlying the enlarged end of said hole in the support and coacting with the flanged portionto positively clamp the first member and the rivet in a positive eiectrica1 conducting relation, and a second of said corrugations spaced from the first corrugation engaging said shoulder, said rivet rivet having a shank with a tubular portion REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 903,972 Hawley Nov. 17, 1908 2,105,756 Rohmer Jan. 18, 1938 2,305,150 Fearon Dec. 15, 1942 2,315,720 Maliina Apr. 6, 1943 2,324,142 Eklund July 13, 1943 Kalstein Jan. 30, 1945 

